Why was Paris Hilton released after being caught smoking marijuana? The police who sniffed out the drugs in her car were too high to testify!

Las Vegas police arrested Paris for having cocaine in her purse. The police had pulled over her car after they smelled marijuana.
So if I get this right, they were following the smell of marijuana and then pulled over the car, they really must have been quite high themselves....right?
They had to let her go...